The present invention relates to apparatus for breaking up or subdividing stacks of superimposed panels, particularly wooden or composition boards or sheets of plywood which must be fed into the range of a rotary saw blade in a power saw or an analogous machine tool. More particularly, the invention relates to improvements in power saws or analogous machine tools wherein a lifting device carries a stack of superimposed panels and cooperates with a transfer unit to supply desired numbers of superimposed panels or discrete panels into the range of the subdividing or severing tool.
In a machine tool of the above outlined character, it is necessary to control the extent of upward movement of the lifting device in order to ensure that a requisite number of panels will be placed into the range of the transfer unit, and it is further necessary to regulate the extent of back-and-forth movement of the transfer unit in order to reduce to a minimum the length of strokes of the transfer unit. As a rule, such operations are controlled by an attendant who stands or sits adjacent to a control panel with a variety of pushbuttons, knobs, levers or analogous actuating elements for the corresponding prime movers of the machine tool. The extent of upward movement of the lifting device must be changed whenever the operator desires to change the number of panels or boards which are to be moved into the range of the severing tool. In other words, it is necessary to monitor the number of panels which have been lifted into the path of movement of the transfer unit so that the latter can thereupon perform a working stroke and transfer the selected number of panels onto the table or another suitable work support of the machine tool. Analogously, it is necessary to monitor the length or width of the panels and to change the strokes of the transfer unit whenever the corresponding dimensions of the panels are changed to thus ensure that the transfer unit will perform return strokes whose length is just sufficient to enable the transfer unit to advance the selected number of superimposed panels (or a single panel) from the top portion of the stack on the lifting device onto the table (namely, into the range of the comminuting or severing tool) while the transfer unit performs its forward stroke.
The above outlined operations must be carried out by a conscientious operator in order to avoid damage to the workpieces and/or to parts of the machine tool, or injury to attendants. Furthermore, the work is time-consuming if the operator is not familiar with the operation of the controls because he or she is likely to cause the transfer unit to perform strokes of excessive length with attendant lengthening of intervals between successive severing operations.